The ducts of Muller in the embryo are destined to form vagina, uterus, and Fallopian tubes, and they are at first double from end to end. The fusion of the ducts occurs soon at their lower extremities so that the vagina and lower part of the uterus early form a single canal. Up to the end of the third month, however, the uterus possesses two horns, the subsequent fusion proceeding from below upwards. In many animals this bilateral duplicity persists during life, so that the adult uterus has two horns, often of great length. The duplicity may persist in different degrees in the human subject presenting various forms.
Uterus Separatus Didelphys is the most extreme degree of duplicity. The ducts have remained separate, so that from the fimbriated extremities of the tubes to the external orifice of the vagina there are two separate canals. The canals may be partially adherent externally, but their walls have not coalesced and they appear externally as two separate tubes. This malformation does not occur except with other deformities, most frequently with extensive fission of the abdomen, and the foetus does not survive.
In this, which is not an uncommon form, there is externally one vagina, which may or may not be divided by a septum, but there are two uteri, which may, however, be united externally in their lower parts. Each uterus has a distinct cervix and os, and each is capable of utero-gestation. Even in cases where the bodies are completely separated (as in Fig. 448) the unimpregnated uterus enlarges with the other.
In the case of which Fig. 448 is an illustration death occurred a fortnight after delivery. Both organs were enlarged and almost equally so, the one which had borne the foetus measuring 4 1/2 inches from os to fundus and the other 4 1/4 There had been a previous pregnancy, and this had probably been in that which had not borne the fjptus on this occasion. This was inferred from the fact that this uterus had adhesions around it and a hsematocele on its posterior wall.
In this the parts appear single externally, but the cavity of the uterus is divided by a septum which may or may not be continued into the vagina.
Fig. 448. - Uterus duplex bicorni.s. The cavities are opened from behind. Foetation has occurred in the right, but the left had also enlarged. The hematocele seen attached to the left may have been from a former fcetation. (From a preparation in Museum of Western Infirmary).
There is one cavity in the lower part of the uterus, but at the fundus the parts diverge. In some cases there is a mere depression in the middle of the fundus, so as to give the organ somewhat of a heart shape, in which case the term uienu orauitus is used, from the bowed or bent character of the outline.
Uterus Subseptus is a form in which the uterus, externally single is partially divided within by a septum.
Kussmaul, Mangel, Verkuuimerung und Verdoppelung der Gebar-mutter, 1859; Mayrhofer, in Billroth's Handb. der Frauenkrank., vol. i., part 2.